/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.hive.ql.udf;

import org.apache.hadoop.hive.ql.exec.NumericUDAF;
import org.apache.hadoop.hive.ql.exec.UDAFEvaluator;



public class UDAFSum extends NumericUDAF implements UDAFEvaluator {

  private double mSum;
  private boolean mEmpty;
  
  public UDAFSum() {
    super();
    init();
  }

  public void init() {
    mSum = 0;
    mEmpty = true;
  }

  public boolean iterate(Double o) {
    if (o != null) {
      mSum += o;
      mEmpty = false;
    }
    return true;
  }
  
  public Double terminatePartial() {
    // This is SQL standard - sum of zero items should be null.
    return mEmpty ? null : new Double(mSum);
  }

  public boolean merge(Double o) {
    if (o != null) {
      mSum += o;
      mEmpty = false;
    }
    return true;
  }

  public Double terminate() {
    // This is SQL standard - sum of zero items should be null.
    return mEmpty ? null : new Double(mSum);
  }

}
